When is it right to reveal an anonymous source?

Few contracts are more inviolable than a reporter's pledge of confidentiality. Some journalists have even been willing to go to jail to protect that principle. But are there occasions when public interest demands that a news organization disclose the name of a confidential source?

After hearing Oliver North's testimony, Newsweek decided yes. North had justified the Administration's widespread deception of Congress by claiming that members often leaked sensitive information. When pressed for examples, he cited stories before the 1986 U.S. raid on Libya and ones detailing the 1985 interception of an Egyptian plane carrying the hijackers of the Achille Lauro. That...